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Old School Bell

zeppssgtr

Jul 19, 2012
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Hi, I recieved what looks like an old school bell from my girl friends father which he wants to get working. I am an electrician however do not know the wiring from this bell. It is a large bell so not sure the voltage? Also, how would i wire this baby up? On the back appears a transformer or capacitor with 2 wires going to the magnets? There are no power wires on it.

2012-07-19_07-57-05_531.jpg


2012-07-19_07-57-24_476.jpg
 

mechtronics

Aug 7, 2011
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looks like a capacitor.
positive and negative supply to red and black wire should do it.

what ever voltage is another thing!!
 
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zeppssgtr

Jul 19, 2012
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No. Both wires coming out if the capacitor go to each magnet. Then one black wire goes from one magnet side to the other magnet
 

mechtronics

Aug 7, 2011
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that would be supplying power to each coil id say. or else its a common ground wire.
 
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mechtronics

Aug 7, 2011
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thats my judgement of it anyway. it would be a DC voltage u'd apply i reckon.
 

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CocaCola

Apr 7, 2012
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Yeah, it appears to simply be two magnets, energize it with some low voltage DC, I would start at 3 and move up to 12 or 18, it's likely not all crucial the higher voltages will just make the frequency higher... The magnets should flip flop as the 'ringer' breaks and makes contact as it moves from side to side...
 

zeppssgtr

Jul 19, 2012
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Tried that many times, but the arm just hits the bell once, does not repeat
 

zeppssgtr

Jul 19, 2012
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It is also a very large bell. The bells are 6" in diameter each, could it take more voltage?
 

CocaCola

Apr 7, 2012
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I would not even attempt feeding it 120v, take your battery and pulse the current, aka tap the connection fast... If that works it wants a pulsed DC or AC current...

If your low voltage battery is energizing the coil enough to activate there is no way you need 120v...
 

gorgon

Jun 6, 2011
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Could it be that the hammer is breaking the contact to one magnet and making to the other magnet for driving the other way? The capacitors could be noise reduction or timing elements.

If driven by AC the frequency need to be very low, due to all the weight needed to move.

TOK ;)
 

CocaCola

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Hmm, how would a use pulsed DC?

Is it working with pulsed DC? Is the hammer flipping from side to side as you pulse in the current?

If so you should be able to get away with a simple 555 timer circuit to drive it, that is if the pulsed DC is working... You might need to beef up the output of the 555 with a transistor though vs driving directly...
 
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mechtronics

Aug 7, 2011
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or maybe the circuit that was originally feeding the bell had a circuit that done the job. as cocacola said u would have to pulse DC if thats the case.
 

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
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My guess is it's a telephone bell. If so, it will be designed to run from a 20 Hz sinewave at around 100V. I wouldn't connect it to the mains; the frequency is much too high and it will overheat because the clapper can't move that fast.

I'm not sure whether this will help you, but I designed a circuit to drive a similar bell using a centre-tapped mains transformer in reverse. Here's the schematic. I used a lot of shorthand in the component values; let me know if you want more details. This should give you the general idea though.

Power comes in on CN1. I used about 30V DC unregulated, from a 24VAC transformer with bridge and plenty of smoothing. U3 creates a 12V rail for U1 and U2. U1 oscillates at a higher frequency than the bell clapper moves at; U2 divides the frequency by ten and provides two short pulses at opposite halves of the cycle, which activate MOSFETs Q1 and Q2, which are used as a crude push-pull driver to energise the drive transformer connected to CN2 one way or the other. The transformer was probably something like 110V input, 24-0-24 output. It's connected in reverse, i.e. the secondary is driven from CN2 and the primary is connected to the bell.

You adjust the oscillator frequency for the best efficiency and loudest noise from the bell. Bells can be very loud, and the sound carries a long way. I think they're better than sirens as alarms and alerts.

Let me know if you want to pursue this and I can give more details.
 

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davenn

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Sep 5, 2009
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get a mains 120/240VAC ( whatever your country uses) to 12 or 24VAC plugpack

and you will be in business

Dave
 
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